The present invention relates to an apparatus for everting a flexible tube liner into the interior of a conduit or pipe, such as a previously existing underground sewer pipe.
One of the more successful pipe repair or rehabilitation processes which is currently used is called the Insituform Process and is described in U.S. Pat. No. 4,009,063, Wood; 4,064,211, Wood, and 4,135,958, Wood, the contents of which are incorporated herein by reference. The method of eversion of a flexible liner as set forth in U.S. Pat. No. 4,064,211 usually required a twenty to thirty foot scaffold to support a vertical flexible tube and connecting pipes that would provide the necessary hydraulic pressure to evert a flexible liner. A number of self-contained, transportable apparatus that used self-erecting tubes and conveyors have been developed, some of which are disclosed in U.S. Pat. No. 4,668,125, Long, Jr., and U.S. Pat. No. 4,685,983, Long, Jr. Recently, U.S. Pat. No. 5,154,936, Driver et al., disclosed an apparatus that everts a flexible tube liner into the interior of a pipe or conduit by an apparatus that is made up of two pipe chambers defining two pressure regions separated by a sphincter-type valve that utilizes a pressure chamber and utilizes external air pressure to cause a flexible tube to impinge upon the flexible liner, resulting in a seal which allows the flexible liner to slide through. The use of this apparatus has been successful. However, the total size and weight of the unit sometimes presents a problem. Since the eversion tube assembly that must pass through the sphincter valve usually includes a bulky or otherwise discontinuous portion, as where the tube itself is connected to a hold-back line and a lay-flat hose which must also sealingly slide through the valve, the passage of that bulky portion through the valve without losing the sealing effect of the valve presents a very real problem. In addition, since in the apparatus of U.S. Pat. No. 5,154,936 the chamber which develops the pressure exerted on the sphincter valve comprises an outer portion defined by the overall rigid structure of the apparatus, the flexible portion of the sphincter valve is relatively inaccessible, making repair or replacement of the sphincter valve a major, and therefore expensive, operation.